A continuing security problem in the world today relates to shipping containers and transportation trailers. Highly valuable contents are secured by locks that are easily picked or cut off by professional burglars. The existing solution is an expensive, non-reusable lock that is nevertheless vulnerable to experienced thieves.
The lock of the present invention combines a unique structure that prevents cut-offs with friction masking and false notches to make a cut-off-proof, pick-proof lock that is simple, rugged, and effective.
Friction-masking is provided by eight (8) o-rings, one in front and back of each of four tumblers. The o-rings are trapped in counterbored rabbets in the lock body. When the lock is assembled, the tumbler from the front is press-fit with a retention pin coming into the lock body from the back, thus compressing both o-rings from both sides. The amount of compression on the o-rings is regulated by the depth of the rabbets in the lock body.
In most mechanical devices, o-rings are provided for fluid sealing. That is not the case here, as the sole purpose for compressing the o-rings on both ends of the tumblers is instead to dampen or remove the frictional feel of metal to metal that is created when the tumblers interact with the locking pin. Without the friction-masking provided by the compressed o-rings, there is a straight metal-to-metal feel when turning the tumblers, which greatly enhances a burglar's chance of gaining entry to the lock.
Viton.TM. o-rings must be used because they are resistant to all acids, solvents, petroleum products, heat, and cold, plus being extremely durable.
When the o-rings are compressed, all metal-to-metal feel is removed. The only way anything is felt is by pulling the locking pin out with great pressure. When this is done, the notches on some of the tumblers can be felt. To remedy this problem, we have cut the "unlock" notch of the tumbler with an end mill which has the same diameter of the locking pin, for example 3/8 inch, and we have also cut five additional false notches in the tumbler with a much smaller diameter end mill, for example 1/8 inch. The key, however, is to have all six notches the same length, which makes it impossible to tell the difference by feel. If the notches were not cut in the tumbler the same length distance, then there would not be the same feel on each and every one of them.
With the combination of the compressed o-rings and the false notches having the same length as the real notches, we have created a lock that we feel is absolutely impossible to open without the correct combination of numbers. In addition, when the o-rings under the tumblers are compressed, the tumblers are hard to turn. By doing this the lock gains additional advantages. The o-rings require that the tumblers on this lock be machined from hexagon stock, leaving the hexagon head as the only external part of the tumbler. This design serves two very useful purposes. The first being that, because of the o-rings, a wrench is required to turn the tumblers. The great advantage in this is in sub-freezing weather or extremely dirty conditions or if the lock has been damaged from physical attack. By using the wrench, the lock will still operate. The second great advantage is that these heads, as opposed to a dials or knobs on all other combination locks, cannot be easily damaged from physical attack or adverse weather conditions. It would be almost impossible to damage one of these heads to the point it would not operate.
The combination of the compressed o-rings, false and real notches all having the same length, and the hexagon heads on the tumblers makes this the most unique, most durable and best lock on the market today.
When combined with a cut-off-proof structure, the lock meets every need and is unremovable except with the right combination or a welding torch. The cut-off-proof structure will now be described.
The only single pin lock in use anywhere in the world to our knowledge, is not a lock, but rather a casehardened bolt that is put through the hasp of trailers and containers and then there is a head press fined on the end with a special tool. This is the lock used by almost all shipping companies worldwide today. There are two large draw-backs to using this type of lock, one is, it can only be used once, because when the shipment gets to its destination it has to be cut off with a large set of bolt cutters. This causes a big inconvenience for the shipper and receiver. The other drawback is the bolt is so hard and brittle that a burglar can put a large wrench or cheater pipe on it and bend it just a little and it will break. Our lock, on the other hand, has a stainless steel locking pin that will bend but not break. Stainless steel has one of the highest tensile strengths of any metal but yet is not brittle. Another great advantage of using a single locking pin such as ours is the fact that the neck can be made any length to custom fit any existing hasp yet leave no room for thieves to cut it off with bolt cutters, etc. No other lock in use today, to our knowledge, possesses this advantage.